1. Field of the Invention
The present invention relates to a member separating apparatus and method and a method of manufacturing a semiconductor substrate.
2. Description of the Related Art
A substrate (SOI substrate) having an SOI (Silicon On Insulator) structure is known as a substrate having a single-crystal Si layer on an insulating layer. A device using this SOI substrate has many advantages that cannot be achieved by ordinary Si substrates. Examples of the advantages are as follows.
(1) The integration degree can be increased because dielectric isolation is easy.
(2) The radiation resistance can be increased.
(3) The operating speed of the device can be increased because the stray capacitance is small.
(4) No well step is necessary.
(5) Latch-up can be prevented.
(6) A complete depletion type field effect transistor can be formed by thin film formation.
Since an SOI structure has the above various advantages, researches have been made on its formation method for several decades.
As one SOI technology, the SOS (Silicon On Sapphire) technology by which Si is heteroepitaxially grown on a single-crystal sapphire substrate by CVD (Chemical Vapor Deposition) has been known for a long time. This SOS technology once earned a reputation as the most matured SOI technology. However, the SOS technology has not been put into practical use to date because, e.g., a large amount of crystal defects are produced by lattice mismatch in the interface between the Si layer and the underlying sapphire substrate, aluminum that forms the sapphire substrate mixes in the Si layer, the substrate is expensive, and it is difficult to obtain a large area.
An SOI technology using a buried oxide layer has appeared next to the SOS technology. For this SOI technology, various methods have been examined to reduce crystal defects or manufacturing cost. The methods include a SIMOX (Separation by Ion iMplanted OXygen) method of ion-implanting oxygen into a substrate to form a buried oxide layer, a method of bonding two wafers via an oxide film and polishing or etching one wafer to leave a thin single-crystal Si layer on the oxide film, and a method of ion-implanting hydrogen to a predetermined depth from the surface of an Si substrate having an oxide film, bonding the substrate to another substrate, leaving a thin single-crystal Si layer on the oxide film by heating or the like, and peeling one (the other substrate) of the bonded substrates.
The present applicant has disclosed a new SOI technology in Japanese Patent Laid-Open No. 5-21338. In this technique, a first substrate obtained by forming a non-porous single-crystal layer (including a single-crystal Si layer) on a single-crystal semiconductor substrate having a porous layer is bonded to a second substrate via an insulating layer (SiO2). After this, the substrates are separated at the porous layer, thereby transferring the non-porous single-crystal layer to the second substrate. This technique is advantageous because the film thickness uniformity of the SOI layer is good, the crystal defect density in the SOI layer can be decreased, the surface planarity of the SOI layer is good, no expensive manufacturing apparatus with special specifications is required, and SOI substrates having about several hundred xc3x85 to 10-xcexcm thick SOI films can be manufactured by a single manufacturing apparatus.
The present applicant has also disclosed, in Japanese Patent Laid-Open No. 7-302889, a technique of bonding first and second substrates, separating the first substrate from the second substrate without breaking the first substrate, smoothing the surface of the separated first substrate, forming a porous layer again on the first substrate, and reusing this substrate. Since the first substrate is not wasted, this technique is advantageous in largely reducing the manufacturing cost and simplifying the manufacturing process.
For example, in the method described in Japanese Patent Laid-Open No. 5-21338, i.e., the method in which a substrate (to be referred to as a bonded substrate stack hereinafter) obtained by bonding a first substrate having a non-porous layer such as a single-crystal Si layer on a porous layer to a second substrate via an insulating layer is separated at the porous layer, thereby transferring the non-porous layer formed on the first substrate side to the second substrate, the technique of separating the bonded substrate stack is very important.
For example, in separating the bonded substrate stack, if it is separated at a portion except the porous layer as the separation layer, the non-porous layer (e.g., a single-crystal Si layer) to be used as an active layer is broken, and no desired SOI substrate can be obtained.
The present invention has been made in consideration of the above situation, and has as its object to prevent any defects in separating a disk-like member such as a bonded substrate stack.
According to the first aspect of the present invention, there is provided a separating apparatus for separating a disk-like member having a separation layer inside, characterized by comprising a holding mechanism for holding the disk-like member while rotating the disk-like member about an axis perpendicular to the separation layer, and a fluid ejection portion for injecting a stream of fluid into the separation layer of the disk-like member held by the holding portion to separate the disk-like member at the separation layer by the fluid, wherein when separating a peripheral portion of the disk-like member, a rotational direction of the disk-like member, a moving direction of the fluid, and a position of the ejection portion are maintained to satisfy a condition in which the moving direction component of the velocity of the disk-like member at an injection position of the fluid to the disk-like member has a negative value.
In the separating apparatus according to the first aspect of the present invention, for example, when separating the peripheral portion of the disk-like member, the ejection portion preferably ejects the fluid having pressure at which an outermost peripheral portion of the disk-like member is separated from an inside to an outside by the fluid injected into the disk-like member.
The separating apparatus according to the first aspect of the present invention preferably further comprises, e.g., a control section for controlling the pressure of the fluid ejected from the ejection portion.
In the separating apparatus according to the first aspect of the present invention, the control section preferably changes the pressure of the fluid in accordance with, e.g., progress of separation processing.
The separating apparatus according to the first aspect of the present invention preferably further comprises, e.g., a driving mechanism for moving the ejection portion along the separation layer.
In the separating apparatus according to the first aspect of the present invention, for example, when separating the peripheral portion of the disk-like member, the driving mechanism preferably adjusts the position of the ejection portion such that the fluid is injected into the peripheral portion, and when separating a center of the disk-like member, the driving mechanism preferably adjusts the position of the ejection portion such that the fluid is injected into the center.
In the separating apparatus according to the first aspect of the present invention, the separation layer is preferably, e.g., more fragile than remaining portions of the disk-like member.
In the separating apparatus according to the first aspect of the present invention, the separation layer is preferably, e.g., a porous layer.
In the separating apparatus according to the first aspect of the present invention, the separation layer is preferably, e.g., a porous layer having a multilayered structure.
According to the second aspect of the present invention, there is provided a separating apparatus for separating a disk-like member having a separation layer inside, characterized by comprising a holding portion for holding the disk-like member, and a fluid ejection portion for injecting a stream of fluid to the separation layer of the disk-like member held by the holding portion to separate the disk-like member at the separation layer by the fluid, wherein when separating a peripheral portion of the disk-like member, separation processing is executed under a condition in which an outermost peripheral portion of the disk-like member is separated from an inside to an outside of the disk-like member by the fluid injected into the disk-like member.
In the separating apparatus according to the second aspect of the present invention, the holding portion preferably has, e.g., a rotation mechanism for holding the disk-like member while rotating the disk-like member.
According to the third aspect of the present invention, there is provided a separating method of rotating a disk-like member having a separation layer inside about an axis perpendicular to the separation layer and ejecting a stream of fluid from an ejection portion into the separation layer to separate the disk-like member at the separation layer by the fluid, characterized by comprising the peripheral portion separation step of separating a peripheral portion of the disk-like member when a rotational direction of the disk-like member, a moving direction of the fluid, and a position of the ejection portion satisfy a condition in which the moving direction component of the velocity of peripheral portion of the disk-like member at an injection position of the fluid to the disk-like member has a negative value, assuming the moving direction of the fluid in the positive direction.
In the separating method according to the third aspect of the present invention, the peripheral portion separation step preferably comprises, e.g., ejecting, from the ejection portion, the fluid having pressure at which an outermost peripheral portion of the disk-like member is separated from an inside to an outside by the fluid injected into the disk-like member.
The separating method according to the third aspect of the present invention preferably further comprises, e.g., the control step of controlling the pressure of the fluid ejected from the ejection portion.
In the separating method according to the third aspect of the present invention, the separation layer is preferably, e.g., more fragile than remaining portions of the disk-like member.
In the separating method according to the third aspect of the present invention, the separation layer is preferably, e.g., a porous layer.
In the separating method according to the third aspect of the present invention, the separation layer is preferably, e.g., a porous layer having a multilayered structure.
According to the fourth aspect of the present invention, there is provided a separating method of holding a disk-like member having a separation layer inside, ejecting a stream of fluid from an ejection portion, and injecting the fluid into the separation layer to separate the disk-like member at the separation layer by the fluid, characterized by comprising the peripheral portion separation step of separating a peripheral portion of the disk-like member under a condition in which an outermost peripheral portion of the disk-like member is separated from an inside to an outside of the disk-like member by the fluid injected into the disk-like member.
In the separating method according to the fourth aspect of the present invention, the peripheral portion separation step preferably comprises, e.g., executing separation processing while rotating the disk-like member bout an axis perpendicular to the separation layer.
According to the fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor substrate, characterized by comprising the step of preparing a first substrate having a porous layer inside and a non-porous layer on the porous layer, the step of bonding the first substrate and a second substrate via the non-porous layer to form a bonded substrate stack, and the separation step of separating the bonded substrate stack into two substrates at the porous layer while rotating the bonded substrate stack about an axis perpendicular to the porous layer and ejecting a stream of fluid and injecting the fluid into the porous layer, wherein the separation step comprises the peripheral portion separation step of separating a peripheral portion of the bonded substrate stack when a rotational direction of the bonded substrate stack, a moving direction of the fluid, and a position of the ejection portion satisfy a condition in which the moving direction component of the velocity of the bonded substrate stack at an injection position of the fluid to the bonded substrate stack has a negative value.
According to the sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor substrate, characterized by comprising the step of preparing a first substrate having a porous layer inside and a non-porous layer on the porous layer, the step of bonding the first substrate and a second substrate via the non-porous layer to form a bonded substrate stack, and the separation step of separating the bonded substrate stack into two substrates at the porous layer while ejecting a stream of fluid and injecting the fluid into the porous layer, wherein the separation step comprises the peripheral portion separation step of separating a peripheral portion of the bonded substrate stack under a condition in which an outermost peripheral portion of the bonded substrate stack is separated from an inside to an outside of the bonded substrate stack by the fluid injected into the bonded substrate stack.